Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using namespace std;
int H,W,white,cnt,dx[]={0,0,1,-1},dy[]={1,-1,0,0},i,j,x,y;
char s[55][55];
struct P{int x,y,c;}t;
queue<P>q;
int main(){
  cin>>H>>W;
  for(i=1;i<=H;i++){
    scanf("%s",s[i]+1);
    for(j=1;j<=W;j++)if(s[i][j]=='.')white++;
  }
  if(s[1][1]=='.')q.push({1,1,1});
  while(!q.empty()){
    t=q.front();q.pop();
    if(t.x==H&&t.y==W){
      cnt=t.c;
      break;
    }
    for(i=0;i<4;i++){
      x=t.x+dx[i];
      y=t.y+dy[i];
      if(s[x][y]=='.'){
        q.push({x,y,t.c+1});
        s[x][y]='#';
      }
    }
  }
  cout<<(cnt?white-cnt:-1)<<endl;
}